I love the polar alignment wizard, but recently have been having an issue with taking the three images. The very first time I start it, the image seems to be 1s exposure regardless of what I have set, so I stop and restart, then the exposure is the correct length.
The 1st exposure is then solved and the mount moves. The 2nd exposure is then started, but always fails with "Cannot capture while CCD exposure is in progress. Retrying in 10 seconds...". Some times it does continue in about 10s, but most of the time it is a lot longer, a couple of minutes or more. Then once this has actually got an image and solved, I get the same for the third image.
At this point all I have done is start kstars, connected to my equipment profile, gone to polar alignment, selected my guide scope and set the exposure to 3s. No other cameras are taking images to the best of my knowledge.

Apologises for lack of debug information, but I cant find the post that tells me what to supply. I swear I have seen one some where?!

Updated KStars (Windows) from 3.3.7 mid-October (not official build) to 3.3.7 Nov 13 (official release). All of a sudden Polar Alignment worked as it should!
Great!
Again, it was working well on RPI client but acting up on Windows client. At least for me.

We're all here to help, given if we can. I see that you are able to capture and solve images and you are running to a windows machine.
How is your network connection? Perhaps lag is an issue.
Is autoguiding attempting to use the camera at the same time?
What is the behaviour when you tree take an exposure and or preview exposure in the capture module?

Often, when you start Ekos, both cameras get assigned as Primary scopes.
Try this and it might help:
When you start Ekos and INDI Control Panel pops-up,
make sure that your main camera is set to Primary (in Options) and
your Guide camera is set to Guide.

Thanks for the replies.
@Ihoujin, I am running on a raspberry Pi4, and just using VNC from Windows, so it is running everything local to the Pi, so I can't see this being an issue. I did check to see if I could spot anything else that might be using the Camera, but could not spot anything, alos what would intermittently start using and then stop using the camera?

@maxthebuilder, I had fallen foul of not setting primary or guide to match the actual camera in the past when solving, but it is now something I always double check, or am I misunderstanding what you are saying?

I had three clear hours last night and spent two trying to work out what is going on with polar alignment. I did check the code base and the error is only raised if the camera returns "is busy", but I cannot work out why it would be busy (and for random amount of times)? Can anyone suggest how to log camera usage? Unfortunately the forecast for the next 7 days is cloudy, and I'm off to a star party on Thursday (Kelling Heath), so dead cert it wont be clear! As mentioned before a couple of months ago it worked fine, but maybe I have set something without realising.

I think I have solved it, but cannot at this point say 100% what the issue was, as I broke the cardinal rule and changed more than one thing!

I have been attempting for the last two hours to start the polar alignment wizard to coincide with a patch of clearish sky, I must have attempted about thirty times just to get as far as the second capture, which is now working instantly, yay.

I eventually managed three consecutive full polar alignment wizards, getting closer and closer to zero each time, third one being 12 arcseconds off, which I think is acceptable!

I think the main problem, which I am still not sure if it should be a problem or not, is that I had my guide camera in my device profile set to Altair, and a second Altair driver in my AUX devices. The reason being I have two altair cameras, one which is used as a standard guider and the second used as a polemaster equivalent. The reason I did this is because I had come across a post where someone asked how to do almost exactly what I was doing, but the subtle difference being their cameras required different drivers.

In the past I have removed one of the cameras, but didn't think to remove the driver. Then tonight I removed the AUX Altair driver, and restarted Kstars and was surprised to see both cameras were still picked up.

I will try to prove this when I get another clear night (totally clouded over now), by adding the Altair back into the AUX devices.